# Autofluorescence

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Natural emission of light by biological structures

[Micrograph](/source/Micrograph) of paper autofluorescing under [ultraviolet](/source/Ultraviolet) illumination. The individual fibres in this sample are around 10 [μm](/source/Micrometre) in diameter.

**Autofluorescence** is the natural [fluorescence](/source/Fluorescence) of biological structures (**autofluorophores**)[1] such as [mitochondria](/source/Mitochondria) and [lysosomes](/source/Lysosome), in contrast to fluorescence originating from artificially added fluorescent markers ([fluorophores](/source/Fluorophore)).[2]

The most commonly observed autofluorescencing molecules are [NADPH](/source/NADPH) and [flavins](/source/Flavin_group); the [extracellular matrix](/source/Extracellular_matrix) can also contribute to autofluorescence because of the intrinsic properties of [collagen](/source/Collagen) and [elastin](/source/Elastin).[2]

Generally, proteins containing an increased amount of the [amino acids](/source/Amino_acid) [tryptophan](/source/Tryptophan), [tyrosine](/source/Tyrosine), and [phenylalanine](/source/Phenylalanine) show some degree of autofluorescence.[3]

Autofluorescence also occurs in non-biological materials found in many papers and textiles. Autofluorescence from U.S. paper money has been demonstrated as a means for discerning counterfeit currency from authentic currency.[4]

## Microscopy

A [multispectral](/source/Multispectral) image of tissue from a [mouse](/source/Mouse)  intestine, showing how autofluoresce can obscure several fluorescence signals.

Autofluorescence can be problematic in [fluorescence microscopy](/source/Fluorescence_microscopy). Light-emitting [stains](/source/Staining) (such as fluorescently labelled [antibodies](/source/Antibody)) are applied to [samples](/source/Sample_(material)) to enable visualisation of specific structures.

Autofluorescence interferes with detection of specific fluorescent signals, especially when the signals of interest are very dim — it causes structures other than those of interest to become visible.

In some microscopes (mainly [confocal microscopes](/source/Confocal_microscope)), it is possible to make use of different lifetime of the [excited states](/source/Excited_state) of the added fluorescent markers and the endogenous molecules to exclude most of the autofluorescence.

Autofluorescence super resolution microscopy/optical nanoscopy image of cellular structures that are invisible with confocal light microscopy

In a few cases, autofluorescence may actually illuminate the structures of interest, or serve as a useful [diagnostic](/source/Diagnosis) indicator.[2]

For example, cellular autofluorescence can be used as an indicator of [cytotoxicity](/source/Cytotoxicity) without the need to add fluorescent markers.[5]

The autofluorescence of human [skin](/source/Skin) can be used to measure the level of [advanced glycation end-products](/source/Advanced_glycation_end-product) (AGEs), which are present in higher quantities during several human [diseases](/source/Disease).[6]

Autofluorescence in [banana](/source/Banana) skin under different light conditions.

[Optical imaging](/source/Optical_imaging) systems that utilize [multispectral](/source/Multispectral) imaging can reduce signal degradation caused by autofluorescence while adding enhanced [multiplexing](/source/Multiplexing) capabilities.[7]

The [super resolution microscopy](/source/Super_resolution_microscopy) [SPDM](/source/Vertico_SMI) revealed autofluorescent cellular objects which are not detectable under conventional fluorescence imaging conditions.[8]

## List of dominant autofluorophores

- Group Molecule Excitation (nm) Fluorescence (nm) Peak Animals (Zoae) Fungi Plants Reference NAD(P)H 340 450 Z F P [9] Chlorophyll 465–665 673–726 P Collagen 270–370 305–450 Z [9] Retinol 500 Z F P [10] Riboflavin 550 Z F P [10] Cholecalciferol 380–460 Z [10] Folic acid 450 Z F P [10] Pyridoxine 400 Z F P [10] Tyrosine 270 305 Z F P [3] Dityrosine 325 400 Z [3] Excimer-like aggregate (collagen) 270 360 Z [3] Glycation adduct 370 450 Z [3] Indolamine Z Lipofuscin 410–470 500–695 Z F P [11] Lignin (a polyphenol) 335–488 455–535 P [12] Tryptophan 280 300–350 Z F P Flavin 380–490 520–560 Z F P Melanin 340–400 360–560 Z F P [13] Nicotinamides Unbound NADH 250–300 and 300–380 420–480 [1] Unbound NADPH Protein-bound NADH Blue shifts ≈20 nm compared to its unbound form Blue shifts ≈20 nm compared to unbound form Protein-bound NADPH Flavins Riboflavin (Vitamin B2) 210–290 and 325–490 480–625 and 490–600 Flavin mononucleotide (FMN) Flavin adenine dinucleotide (FAD+) Collagens Types 1-28 250–450[14] 250–550[14] Porphyrins Coproporphyrin I ≈360–440 580–730 Protoporphyrin IX 350–650 580–730 Aromatic amino acids Tyrosine 250–325 300–400 and 500–600 Tryptophan 250–310 300–425 Dityrosine 250–350 350–410 Elastin 300–480 450–650 A2E 250–550 500–750 Lipofuscin 320–480 400–700 Melanin 350–600 450–800 Keratin 365–460 410–600 Retinols Retinol 250–380 414–550 Retinol-binding protein (RBP) bound to retinol 260–400 250–575 Unbound RBP 250–575

- Substances luminous in animal tissue are, by taxonomic inclusion, also luminous in [human](/source/Hominid) tissue.

## See also

- [Autoluminescence](https://en.wiktionary.org/wiki/autoluminescence)

- [Phosphorescence](/source/Phosphorescence)

- [Fluorescence in the life sciences](/source/Fluorescence_in_the_life_sciences)

## References

1. ^ [***a***](#cite_ref-:0_1-0) [***b***](#cite_ref-:0_1-1) Campbell, Jared M.; Gosnell, Martin; Agha, Adnan; Handley, Shannon; Knab, Aline; Anwer, Ayad G.; Bhargava, Akanksha; Goldys, Ewa M. (2024-06-12). ["Label‐Free Assessment of Key Biological Autofluorophores: Material Characteristics and Opportunities for Clinical Applications"](http://web.archive.org/web/20250611122824/https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/adma.202403761). *Advanced Materials*. **36** (42). [doi](/source/Doi_(identifier)):[10.1002/adma.202403761](https://doi.org/10.1002%2Fadma.202403761). [ISSN](/source/ISSN_(identifier)) [0935-9648](https://search.worldcat.org/issn/0935-9648). Archived from [the original](https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/adma.202403761) on 2025-06-11.

1. ^ [***a***](#cite_ref-Monici-2005_2-0) [***b***](#cite_ref-Monici-2005_2-1) [***c***](#cite_ref-Monici-2005_2-2) Monici, M. (2005). "Cell and tissue autofluorescence research and diagnostic applications". *Biotechnology Annual Review*. **11**: 227–256. [doi](/source/Doi_(identifier)):[10.1016/S1387-2656(05)11007-2](https://doi.org/10.1016%2FS1387-2656%2805%2911007-2). [ISBN](/source/ISBN_(identifier)) [9780444519528](https://en.wikipedia.org/wiki/Special:BookSources/9780444519528). [PMID](/source/PMID_(identifier)) [16216779](https://pubmed.ncbi.nlm.nih.gov/16216779).

1. ^ [***a***](#cite_ref-Menter-2006_3-0) [***b***](#cite_ref-Menter-2006_3-1) [***c***](#cite_ref-Menter-2006_3-2) [***d***](#cite_ref-Menter-2006_3-3) [***e***](#cite_ref-Menter-2006_3-4) Menter, Julian M. (2006). "Temperature dependence of collagen fluorescence". *Photochemical & Photobiological Sciences*. **5** (4): 403–410. [doi](/source/Doi_(identifier)):[10.1039/b516429j](https://doi.org/10.1039%2Fb516429j). [PMID](/source/PMID_(identifier)) [16583021](https://pubmed.ncbi.nlm.nih.gov/16583021). [S2CID](/source/S2CID_(identifier)) [34205474](https://api.semanticscholar.org/CorpusID:34205474).

1. **[^](#cite_ref-4)** Chia, Thomas; Levene, Michael (17 November 2009). ["Detection of counterfeit U.S. paper money using intrinsic fluorescence lifetime"](https://zenodo.org/record/894876). *Optics Express*. **17** (24): 22054–22061. [Bibcode](/source/Bibcode_(identifier)):[2009OExpr..1722054C](https://ui.adsabs.harvard.edu/abs/2009OExpr..1722054C). [doi](/source/Doi_(identifier)):[10.1364/OE.17.022054](https://doi.org/10.1364%2FOE.17.022054). [PMID](/source/PMID_(identifier)) [19997451](https://pubmed.ncbi.nlm.nih.gov/19997451).

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1. **[^](#cite_ref-Ger09_6-0)** Gerrits, E.G.; Smit, A.J.; Bilo, H.J. (March 2009). ["AGEs, autofluorescence and renal function"](https://doi.org/10.1093%2Fndt%2Fgfn634). *Nephrol. Dial. Transplant*. **24** (3): 710–713. [doi](/source/Doi_(identifier)):[10.1093/ndt/gfn634](https://doi.org/10.1093%2Fndt%2Fgfn634). [PMID](/source/PMID_(identifier)) [19033250](https://pubmed.ncbi.nlm.nih.gov/19033250).

1. **[^](#cite_ref-7)** Mansfield, James R.; Gossage, Kirk W.; Hoyt, Clifford C.; Levenson, Richard M. (2005). ["Autofluorescence removal, multiplexing, and automated analysis methods for in-vivo fluorescence imaging"](https://dx.doi.org/10.1117/1.2032458). *Journal of Biomedical Optics*. **10** (4): 041207. [Bibcode](/source/Bibcode_(identifier)):[2005JBO....10d1207M](https://ui.adsabs.harvard.edu/abs/2005JBO....10d1207M). [doi](/source/Doi_(identifier)):[10.1117/1.2032458](https://doi.org/10.1117%2F1.2032458). [PMID](/source/PMID_(identifier)) [16178631](https://pubmed.ncbi.nlm.nih.gov/16178631). [S2CID](/source/S2CID_(identifier)) [35269802](https://api.semanticscholar.org/CorpusID:35269802).

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1. ^ [***a***](#cite_ref-Georgakoudi-Jacobson-etal-2002-02-01_9-0) [***b***](#cite_ref-Georgakoudi-Jacobson-etal-2002-02-01_9-1) Georgakoudi, I.; Jacobson, B.C.; Müller, M.G.; Sheets, E.E.; Badizadegan K.; Carr-Locke, D.L.; et al. (2002-02-01). "NAD(P)H and collagen as *in vivo* quantitative fluorescent biomarkers of epithelial precancerous changes". *Cancer Research*. **62** (3): 682–687. [PMID](/source/PMID_(identifier)) [11830520](https://pubmed.ncbi.nlm.nih.gov/11830520).

1. ^ [***a***](#cite_ref-Zipfel-Williams-etal-2003-06-10_10-0) [***b***](#cite_ref-Zipfel-Williams-etal-2003-06-10_10-1) [***c***](#cite_ref-Zipfel-Williams-etal-2003-06-10_10-2) [***d***](#cite_ref-Zipfel-Williams-etal-2003-06-10_10-3) [***e***](#cite_ref-Zipfel-Williams-etal-2003-06-10_10-4) Zipfel, W.R.; Williams, R.M.; Christie, R.; Nikitin, A.Y.; Hyman, B.T.; Webb, W.W. (2003-06-10). ["Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC165832). *Proceedings of the National Academy of Sciences of the United States of America*. **100** (12): 7075–7080. [Bibcode](/source/Bibcode_(identifier)):[2003PNAS..100.7075Z](https://ui.adsabs.harvard.edu/abs/2003PNAS..100.7075Z). [doi](/source/Doi_(identifier)):[10.1073/pnas.0832308100](https://doi.org/10.1073%2Fpnas.0832308100). [PMC](/source/PMC_(identifier)) [165832](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC165832). [PMID](/source/PMID_(identifier)) [12756303](https://pubmed.ncbi.nlm.nih.gov/12756303).

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1. ^ [***a***](#cite_ref-:1_14-0) [***b***](#cite_ref-:1_14-1) Diverse results in literature varying with type, structure, and preparation method

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Adapted from the Wikipedia article [Autofluorescence](https://en.wikipedia.org/wiki/Autofluorescence) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Autofluorescence?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.